1. Field of Invention
This invention relates to a device and a process for monitoring a machine, especially a wind power plant.
2. Description of Related Art
With condition monitoring (CM), deviations in the running and operating behavior of machines and systems are to be detected in time and dedicated diagnosis messages on the machine state are delivered. The objective of a diagnosis can be a function diagnosis or a damage diagnosis. A function diagnosis relates to measurement of functional and operating parameters which are necessary for proper functioning and for economical operation of machines. Damage diagnosis is defined as determination of the damage state of machines and machine components. This includes all diagnosis measures for determining the degree of wear and its effects, fatigue and corrosion as well as other damaging effects. Complex diagnosis is the determination of the overall state of machines. The complex state is determined using several (complex) characteristics. Deep diagnosis relates to determination of the state of individual assemblies of machines or of the states of individual parts. Accordingly, it constitutes detail checking. Deep diagnoses are therefore used mainly for fault location and for establishing the scope of corrective maintenance before scheduled maintenance.
German Patent Application DE 10 2005 031 436 A1 relates to a process for monitoring fatigue of a wind power plant by means of vibration sensors, the stiffness matrix and inertia matrix being determined in order to detect state changes. European Patent Application EP 1 760 311 A2 describes a process for monitoring the state of a wind power plant by means of sensors attached to the main shaft, and among others, evaluation of fatigue is undertaken. Recommendations for measurement and assessment of mechanical vibrations of wind power plants are also described in VDE Guideline 3834.
Analysis of the type and effect of fault states (FMEA) (also called fault possibility effect analysis) is defined as a certain type of systematic procedure in the analysis of a system in order to determine types of possible fault states, their causes and their effects on system behavior. FMEA processes are used in many industrial domains, for example, also in plant construction, product development, product improvement and in part also in the development of maintenance schedules.
FMECA (analysis of type, effect and criticality of the fault state) designates a case of FMEA in which there is a means for classification of the severity of types of failure of the system in order to enable classification of the urgency of remedial measures. This takes place by combination of a measure for severity with the expected frequency of occurrence in order to produce a metric called “criticality”.
A systematic description of FMEA can be found, for example, in DIN EN 60812.
For quantitative determination of the criticality of system faults or system failures, in FMEA typically a so-called risk priority number (RPZ) is used which follows from the product of the following index quantities: severity of the effect of the occurrence of the fault with respect to the functioning of the system; probability of discovery of the fault (estimated value for the chance of detecting and correcting the fault before the system is affected by the fault); frequency with which the fault occurs within a certain time interval. Typically each of the index quantities is assigned an integral value between 1 and 10.
U.S. Pat. No. 6,968,293 B2 suggests using the FMEA process in conjunction with state monitoring of systems, the application being the monitoring of railroad tracks; the use of risk priority numbers is also mentioned. U.S. Patent 2004/0263342 A1 relates to a process for state monitoring for an electric motor, parameters being monitored which are derived from FMEA fault types, for example, vibrations. U.S. Patent 2007/0050178 A1 relates to risk assessment for the cabling of aircraft, and vibrations can be incorporated into the assessment and the result can be delivered in the form of a FMEA report. DE 10 2004 015 400 A1 corresponds to U.S. Pat. No. 7,249,284 B2 describes a system for evaluating the maintainability of systems which has a FMEA interface. German Patent Application DE 101 39 968 A1 describes an automated FMEA process in which risk priority numbers are also determined.